Objective: This study aims to evaluate the effects of long-term treatment with medical cannabis (MC) on the course of Parkinson’s disease (PD), with a focus on safety.

Background: Over the past decades, cannabis has become widely available for medical use, and in Israel, MC is now commonly approved for pain disorders and other indications including PD as an alternative natural means of symptom control. Regular use of cannabis is associated with increased risk of depression, psychosis, and neuropsychological decline. While studies have demonstrated efficacy of MC for symptoms of PD, its long-term safety has not been investigated in PD, in comparison to an untreated group.

Method: At the Sheba Medical Center Movement Disorders Institute (SMDI) over 256 patients with parkinsonism have been issued a license for using MC for their symptoms. This retrospective case-control observational real-life study included 100 patients with idiopathic PD (mean age at diagnosis: 55.6±9.5 years) followed during 2008-2022. Fifty patients that have used MC for one year or more, were compared to an equal number of matched PD patients with similar sex, age at diagnosis, disease duration, and Hoehn and Yahr (H&Y) stage, who were not treated with MC. Data on levodopa equivalent daily dose (LEDD), H&Y progression and patient-reported outcome measures regarding cognitive impairment, depressive and psychotic symptoms, at baseline and at follow up, were collected from the electronic medical records and were analyzed for differences between groups.

Results: There was no significant difference in the mean annual change in LEDD or H&Y between the MC-treated group and the untreated group (95% CI [-22.47, 70.87 mg/year] and [-0.17,0.02 change/year], P=0.31 and P=0.12, respectively). There was no sign of enhanced deterioration of psychotic, depressive or cognitive symptoms in the MC group, at 1, 2 and 3 years of follow up (P=0.10-0.68) and Kaplan-Meier analyses did not suggest any group difference in the first reported of the above nonmotor symptoms over time (P=0.27-0.93).

Conclusion: These intermediate results suggest that MC, a commonly provided complementary therapy for PD, is safe, regarding neuropsychiatric symptoms, and seems not to have a detrimental effect on disease progression.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/long-term-safety-of-medical-cannabis-in-parkinsons-disease-a-retrospective-case-control-study/